The present invention relates generally to back packs, and is particularly concerned with a back pack having a hard or rigid outer shell.
Traditional back packs are made of fabric or soft material such as canvas, nylon, leather and the like. Disadvantages of such back packs are that they are not particularly durable, do not protect fragile items against impacts or dropping, and can be uncomfortable to wear when the edges of hard items such as books are pressed against the rear wall of the back pack, and thus against the wearer's back. In order to avoid or reduce these problems, some back packs have been made partially or completely of hard or rigid material. One such hard shell back pack is described in U.S. Pat. No. 5,911,348 of Shook. This back pack has a hollow base shell of rigid material with an upper or outer opening closed by a rigid lid which is hinged at one end to the top of the base shell, and releasably secured in a closed position by a latch. It is necessary in this case to place raised cushion pads on the lower wall of the base shell, so that it does not rest directly against the user's back, and the hard material of the shell does not cause discomfort. The mechanical hinge and latch closure of this back pack is not ideal.
U.S. Pat. No. 6,179,186 of Blanking describes a back pack which has a flexible inner wall facing the back of the user, and a dimensionally stable outer shell to protect fragile objects in the back pack from impact. In this back pack, the rigid plastic shell is riveted to the fabric inner wall, and is hinged to pivot into a partially open position with the opening at the top of the back pack. This can make it difficult to retrieve items from the bottom of the back pack, since the pack cannot be fully opened due to the rivets.